This invention relates generally to the heating of liquids, and specifically to those devices wherein rotating elements are employed to generate heat in the liquid passing through them. Devices of this type can be usefully employed in applications requiring a hot water supply, for instance in the home, or by incorporation within a heating system adapted to heat air in a building residence. Furthermore, a cheap portable steam generation could be useful for domestic applications such as the removal of winter salt from the underside of vehicles, or the cleaning of fungal coated paving stones in place of the more erosive method by high-pressure water jet.
Joule, a wealthy Manchester brewer and English physicist who lived during the 19th century, was the first experimenter to show that heat could be produced through mechanical work by churning liquids such as water. Joule""s ideas, as well as the work of others such as Lord Kelvin and Mayer of Germany, eventually led to the Principle of the Conservation of Energy. On the basis of this law, that energy can neither be created nor destroyed, numerous machines have been devised since Joule""s early work. Of the various configurations that have been tried in the past, types employing rotors or other rotating members are known, one being the Perkins liquid heating apparatus disclosed in U.S. Pat. No. 4,424,797. Perkins employs a rotating cylindrical rotor inside a static housing and where fluid entering at one end of the housing navigates past the annular clearance existing between the rotor and the housing to exit the housing at the opposite end. The fluid is arranged to navigate this annular clearance between the static and non-static fluid boundary guiding surfaces, and Perkins relies principally on the shearing effect in the liquid, causing it to heat up.
A modern day successor to Perkins is shown in U.S. Pat. No. 5,188,090. Like Perkins, the James Griggs machine employs a rotating cylindrical rotor inside a static housing and where fluid entering at one end of the housing navigates past the annular clearance existing between the rotor and the housing to exit the housing at the opposite end. The device of Griggs has been demonstrated to be an effective apparatus for the heating of water and is unusual in that it employs a number of surface irregularities on the cylindrical surface of the rotor. Such surface irregularities on the rotor seem to produce an effect quite different effect than the forementioned fluid shearing of the Perkins machine, and which Griggs calls hydrodynamically induced cavitation.
What is certain is that both Perkins and Griggs choose to employ a fixed gap clearance between the rotating rotor and the static housing. The choice thus made means that once the machine is assembled, the clearance cannot be changed. Although changing the clearance can obviously be achieved,through subsequent machine disassembly and substitution of the rotor with one having either a smaller or larger diameter, such an act is both costly and time consuming to perform. Also, once such a machine is installed in its intended application environment, it may turn out not to be best suited for the task at hand, and any subsequent rectification at the site of the application is best avoided if at all possible. An expensive option would be to manufacture a series of machines, each exhibiting a slight variation in the clearance size. However, a better and more advantageous solution would be include the possibility for changing the clearance without having to disassembly the machine. This could also be easily done at the site of the application.
A further problem could occur in the event of any appreciable wear occurring during the design lifetime of the machine. Scale or other impurities that may on occasion pass through the clearance might cause sufficient damage to the surfaces that as a result, there is a noticeable drop in the efficiency of energy conversion. Were this to occur with such fixed clearance devices, the machine would require disassembly and repair. There would be an advantage however, if the damaged surfaces could be readjusted to reduce the operating clearance, thus saving the expense of performing a costly repair.
There therefore is a need for a new solution to overcome the above mentioned disadvantages, and in particular, there would be an advantage if the solution were simple to implement, resulting in an improved and more easily controllable device, and especially whenever possible, without the need for the device to be torn down from the application in order to perform the required alterations/corrections in the event, for instance, a change in the desired operational characteristics of the device be sought for.
A principal object of the present invention is to provide a novel hot water and steam generator capable of producing heat at a high yield with reference to the energy input.
Its is a further object of the invention to use a vector component of the centrifugally induced forces in the liquid towards propelling the liquid through the device, in addition to the impulse on the fluid introduced by the difference in relative velocities of the opposing fluid boundary surfaces. It is therefore a feature of the invention that liquid particles drawn into the annular conduit are not only heated through the shearing action between the opposing fluid boundary surfaces, but are also propelled by such natural forces known in nature to exit the device.
It is a further feature of this invention, as disclosed for certain preferred embodiments, that there be an ability provided whereby the size of clearance between the rotating and stationary elements can be changed without undue complication. Changing the clearance, squeezing the fluid film in the gap between the static and non-static fluid boundary guiding surfaces, introduces a change in the dynamic behaviour of the fluid as it rushes over these surfaces.
There would also be an advantage in being able to take care of a small amount of wear affecting the working clearance of the device, simply and cheaply, by resetting the minimum amount of gap height in the clearance. It is therefore a further object of the invention to provide, when required, provision for the adjustment in the annular clearance between rotor and housing. Furthermore, such an adjustment will allow each machine to be fined tuned and tailor made to suit each particular application.
It is a further aspect of this invention to provide an internal fluid heating vessel chamber for the device in which the radial width dimension changes as soon as the axial length dimension is changed. Therefore, in one form of the invention as described, the annular fluid volume between the rotating rotor and the static housing is changed as soon as the rotor is displaced along its longitudinal rotating axis. By thus altering the annular fluid volume, the shear in the passing fluid is changed. Turbulence and frictional effects experienced in the fluid during its passage through the annular fluid volume can thereby be more easily controlled as compared to prior solutions relying on a fixed clearance between the revolving rotor and the static housing. Accordingly, it is a further object of the invention for the device to provide more flexibility for each particular application and dynamic operational condition, regardless whether the heat output is in the form of a liquid or vapour at various pressures.
In one form thereof, the invention is embodied as an apparatus for the heating of a liquid such as water, comprising a housing having a main chamber. A central member is located in the chamber and moveable relative to the housing about an axis of rotation. The central member is provided with an outer surface and the chamber is provided with an inner surface radially spaced apart such that these surfaces confront each other without touching so thereby defining an annular fluid volume between them. A fluid inlet is arranged to communicate with the annular fluid volume nearer one end of the chamber and where a fluid outlet is arranged to communicate with the annular fluid volume nearer the opposite end of the chamber. At least one of these surfaces is to be angularly inclined with respect to the axis of rotation.
Any relative axial movement between these surfaces will result in a change in the annular fluid volume, expanding or contracting, and where preferably, the central member is a rotor having its smaller diametric end nearer the fluid inlet and the larger diametric end nearer the fluid outlet.
According to the invention from another aspect, the smaller diametric end of the rotor can be formed to include an impeller. The action of the rotating impeller on the fluid entering the chamber being to propel it outwardly and where the axial position of the impeller moves along the longitudinal axis of the drive shaft in accordance with the bodily shifting of the rotor assembly. It is therefore a still further aspect of this invention, as disclosed for certain preferred embodiments, to provide a device of the preceding objects in which the intake of fluid from an external source is excited by an internally driven spinner impeller to substantially raise the pressure of fluid entering the annular fluid volume also termed the fluid heat generating region. By thus increasing the positive head on the fluid as it commences entry to the fluid heat generating region, the running efficiency of the device may thereby be improved.
Applications where mains water pressure can be used, or the source tank is situated well above the height of the device thereby providing a positive head at the fluid inlet, the impeller may be omitted. However, under normal atmospheric conditions with liquid entering the device from a source having a surface level positioned approximately at the same height elevation as the device, the addition of an impeller would better ensure positive priming of the device. In the preferred embodiments used to describe the present invention, such an impeller is shown.